Design of discrete time notch filter for biomedical applications

The challenge in obtaining accurate recordings of biomedical signals such as EEG and ECG is to deal with the interference that is caused due to power line, which is a low frequency signal at 50Hz/60Hz. In order to yield accurate readings from ECG/EEG there is a need to eliminate this interfering signal. This paper presents the design of discrete-time notch filter to eliminate 60Hz, The filter is implemented in CMOS 180nm technology. The Tow-Thomas topology is used for the implementation of the filter which includes fully differential operational amplifier and switched capacitor based resistors. The conventional approach of filter design i.e continuous time approach using resistors consumed large silicon area, hence a discrete time approach is presented in this paper which replaces the resistors by switched-capacitor network. The results of discrete time filter show a notch depth of 62.3dB consuming power of 9.936μΨ. The design is simulated using Cadence Virtuoso and the post layout simulations are presented.